1. Field of the Invention
The subject invention relates to material identification and, more particularly, to material identification using infrared thermometry.
2. Description of the Problem and Prior Art
One of the difficulties encountered in automatic material handling apparatus resides in the fact that typically the apparatus is incapable of identifying the type of material being handled. Inability to distinguish one type of material from another imposes a constraint on the effectiveness of such apparatus since in many applications it is not always completely predictable what type of material will be presented for the next operation. This is particularly true in the use of robots programmed to carry out a sequence of operations in a fixed pattern without the aid of sensors to identify the material being handled. In such operations, the robot is typically programmed to pick up in succession different type sheet material arranged in a stack for separation and further processing. Where, in such applications, the different types of sheet material are not prearranged in the stack as planned or predicted, the inability of the robot to recognize this fact may result in moving the wrong material to the next operation in the sequence.
On the other hand, in some operations the type of material to be handled through the various sequence of operations is not predictable but rather the material may be any one of several types available in random fashion. In such applications, it is desirable to be able to identify the type of material to be moved so that it may be moved to the appropriate location for the next processing step.
Although sensor systems are known for measuring various parameters of materials during processing, no sensor system is known for identifying the type of material being processed. One parameter typically measured during processing is temperature and one common approach to measuring temperature involves use of infrared thermometry. Although infrared thermometry systems are known to be effective to remotely measure temperature of materials, such systems have, heretofore, not been known to be effective to remotely identify different types of material.
Likewise, although sensors are known to optically sense various conditions of the surface of material, no such system has been known to identify the type of material. An example of a typical sensor system that acts to detect the state or condition of the surface of material may be seen by reference to the article entitled "Fibre-Optic Object Sensor" by F. J. Bealle, IBM Technical Disclosure Bulletin, Vol. 23, No. 5, September 1980, pp. 1384-85. Another example may be seen by reference to Baxter et al in an IBM Technical Disclosure Bulletin article entitled "Reflectance Meter", Vol. 11, No. 5, October 1968, pp. 520-21. A further scheme which relies on optical reflectance from the surface of material is that described by C. R. Strife in the IBM Technical Disclosure Bulletin article entitled "Automatic Core Feed", Vol. 13, No. 6, November 1970, pp. 1633-34.
Although these optical reflectance schemes are effective for measuring the condition of the surface of the material, such schemes are ineffective for identifying the type of material being employed. One of the reasons why optical reflectance schemes are not effective to identify the type of material from which the reflection occurs is that optical reflection is not a function of material characteristics indicative of the type of material. For example, two materials with a generally white surface, such as ceramic and paper, would generally provide indistinguishable optical reflectance. Thus, the use of reflected light in the visible range is not effective for identifying types of material.